Tarnish-resisting silver plate and process for producing same



Patented July 9, 1929.

UNITED STATES.

PATENT OFFICE.

DANIEL GRAY AND RICHARD O. BAILEY, OI ONEIDA, AND WILLIAM S. MURRAY, UTICA, NEW YORK, ASSIGNORS TO ONEIDA COMMUNITY, LIMITED, 0] ONEIDA, NEW YORK, A CORPORATION OF NEW YORK.

TARNIBH-RESISTING SILVER PLATE AND PROCESS FOR PRODUCING am.

No Drawing. Application filed November 5, 1923, Serial No. 673,026. Renewed July 86, 1827.

This invention relates to improvements in silver plated articles and to processes for producing the same.

One of the difficulties in the production of such silver-plated articles is that the plating is readily tarnishable, and this is true of pure silver, which is ordinarily used in silver plating, as well as coin and sterling silver which have a silver content of 90% and 92.5% respectively.

This tarnishing of silver-plated ware is a serious inconvenience and a source of expense to dealers and users entailing as it does repeated cleansing of the plating, by

5 rubbing, polishing, etc., which also results in wearing away the plating.

It is the object of the present invention to provide silver-plated articles which will be tarnish resisting and, therefore, free of the objection just referred to.

This is attained by the use of a silveralloy having not less than the silver content of coin or sterling requirements and which will be tarnish resistant because of the tarnish resisting quality or shielding action of its alloy as to tarnishing.

According to the present invention the article to be coated, which may be of any material suitable for the purpose but which is usually of electrically conducting material,

is immersed to the required extent in a solution capable of delivering the silver and the shielding metal in a completely mixed condition and in a continuous coating to the surface of the article to be coated, when such surface is included as a cathode in the plat ing bath.

The shielding metal used for this purpose according to the present invention is mercury.

The present invention includes the use of this in the production of silver alloy platings having a silver content about that existing in coin or sterling silver (90% and 92.5%) or a larger silver content. Infa'ct for silver plating purposes the silver content of the alloy should be as near as possible to that of commercially pure silver, WlllCh is about 99.92%. The relative proportions of silver content and mercu content however may be varied without dbparting from the present invention so long as the silver content is not less than that of coin and sterling silver.

The following example will sufiice for an understanding of the invention, the 'product being a silver plating alloy coating with a silver content of 94.5 and a mercury content of 5.5.

In producing such a lating an aqueous solution is prepared as fgllows, the proport1ons stated being for a one gallon solution.

Mercuric cyanide to contain 1.3 oz. of mercury per gallon. Potassium silver cyanide to contain about 4 oz. of silver per gallon. Potassium cyanide (free) about 6 oz. per gallon. Potassium carbonate about 8 oz. per gallon.

The current for this bath may be generated by any suitable means, such as dynamo or battery. It is necessary to have a rheostat suitable for closely controlling the current and an ammeter for reading its strength. The difierence in potential. between anodes and cathode must be suflicient to deposit mercury.

An insoluble anode is preferably used and the article to be lated being immersed in the solution the si ver and mercury are plated upon it from the solution.

The current should be such as to give a density at the cathode of about 7 amperes per square foot. The anode may be about 2 inches from the cathode. The bath is used at ordinary temperatures.

A plating may be obtained with this bath of any thickness within the requirements of silver-plated ware, the thickness varying with the length of time the cathode is immersed in the.bath and the current density of the bath.

What is claimed is:

1. A silver-plated article in which the plating consists of an intimate mixtureof silver and mercury with a silver content of tion being such as to give a plate having about 90% or over and mercury. about 90% or over of silver content. 10 2. The process of producing an artlcle In testimony whereof, we have hereunto suchas defined by claim 1, which consists set our hands.

5 in preparing a solution wntaining silver and mercury and simultaneously depositing v DANIEL GRAY.

said metals u n the base to be plated, the RICHARD O. BAILEY.

ratio of the s' ver to the mercury in the solu- WILLIAM S; MU RRAY. 

